The present invention relates to a tank closure for the fill opening of a fuel tank, especially for a fuel tank of a portable working tool with an internal combustion engine, the tank closure comprising a closure device penetrating the fill opening and a grip portion for actuating the closure device.
In U.S. Pat. No. 4,113,138 a tank for liquids with a tank closure is disclosed. The tank comprises a fill socket which is provided with an exterior thread. The tank closure is comprised of a substantially cup-shaped component with an interior thread so that the tank closure can be threaded onto the fill socket. The tank closure at its inner side is provided with a sealing comprised of an elastic material whereby the exterior edge of this sealing is clamped between an annular bottom surface of the tank closure and an upper annular surface of the fill socket.
Such a tank closure arrangement requires considerable constructive space in order to allow the arrangement of the corresponding threads required for threading. Corresponding to the number of thread windings the tank closure must be turned a corresponding number of times in order to be threaded onto the fill socket so that finally the sealing is clamped between the respective surfaces and the sealing action is achieved. Such a fill socket with screwed-on tank closure projects substantially past the actual contour of the fuel tank so that such an arrangement is not suitable for small fuel tanks with smooth contours. This is especially true for portable working tools such as, for example, motor chainsaws, trimmers, cutting devices etc. the manipulation of which would be impaired with such projecting fill sockets and tank closures being present.
From U.S. Pat. No. 4,705,190 it is known to arrange a tank closure in a recessed manner so that the tank closure does not project past the outer contour. However, the tank closure in this design is positioned in a recess within the vehicle body whereby between the tank and the tank closure an elongate filling pipe is provided. At the upper end of the filling pipe an inner thread is provided into which the pin-shaped section of the tank closure with external thread is to be threaded. Such an arrangement is also entirely unsuitable for fuel tanks of portable working tools because an elongate filling pipe and also the arrangement of a thread with multiple thread windings for threading the tank closure requires too much space and is detrimental to manipulating the working tool.
It is therefore an object of the present invention to provide a tank closure of the aforementioned kind which is simply insertable into the fill opening of a fuel tank having preferably a substantially smooth contour and which closes off the fuel tank in a reliable manner.